Interpolymers of isoolefine with diolefins and process of producing same



carbamate, etc.

Patented May 25, 1948 INTERPOLYMERS OF ISOOLEFINE WITH DI- OLEFINS ANDPROCESS OF PRODUCING SAME William J. Sparks, Elizabeth,.and Robert M.

Thomas, Union, N. 1., minute, by mesne assignments, to Jason,Incorporated, a corpora- 4 tion of Louisiana No Drawing.

Application August 27, 1941, Serial No. 408,466

8 Claims. (Cl. 260-23) This invention relates to plastic, elasticrubbery materials, relates particularly to high molecular weightsynthetic polymers of an iso-olefln, such as isobutylene, with adiolefin, having a relatively low iodine number; and relates especiallyto a sulfur chloride treatment of a synthetic heteropolymer of aniso-olefln with a diolefin.

It has been found possible to produce interpolymers or copolymers ofiso-olefins such as isobutylene with dioleflns, particularly conjugateddiolefins such as butadiene or isoprene or pentadiene or dimethylbutadiene by the use of a low temperature technique at temperaturesranging from -20 to -100 C. or lower, with a Friedel- Crafts type activemetal halide catalyst such as aluminum chloride or aluminum bromide, insolution in a low freezing solvent such as ethyl or methyl chloride orcarbon disulfide or other similar inert low freezing solvent for theactive metal halide substance. The resultant polymer is composed of amajor amount of polymerized isobutylene molecules with a minor amount ofinterpolymerized diolefin molecules, usually less than preferably lessthan 50%. The polymer is characterized by a relatively low iodinenumber, usually between 1 and 10, and preferably below 45, and arelatively high molecular weight, preferably above 15,000, or even above25,000, up to about 100,000 to 150,000. This polymer is 'reactive withsulfur, especially in the presence of a sulfurization aid, 1. e., asulfur compound of the thiuram type such as tetra methyl thiuramdisulflde or other analogous substances such as dipentamethylene thiuramtetrasulflde, selenium diethyl dithio carbamate, and zinc dibutyl dithioThe sulfurizatlon reaction is a curing procedure having a few points ofsimilarity to the vulcanization of rubber in that it destroys theplasticity of the material and produces in it a definite elastic limitand a definite elongation at break, the tensile strength ranging from2,000 to 4,600 lbs/sq. in. and the elongation ranging from 500% to 1200although under favorable conditions the upper value of the tensilestrength can be substantially increased. The curing reaction preferablyoccurs at temperatures ranging from 145 C. to 180 C. and preferably bythe application of those temperatures for time intervals ranging from 10minutes to 4. hours, depending upon the sulfurization aid, the characterof the polymer, and the temperature.

It is now found, however, that by the procedure of the presentinvention, a'very substantial increase in ilexure resistance andabrasion resistance can be obtained, and the modulus of the materialimproved, and also the material is more easily cured, especially in thepresence of other substances which tend to interfere with the curing ofthe polymer as originally produced.

The present invention consists of a treatment of the olefin polymer, inthe solid form on the mill, heated, if desired, with sulfur chloride.This treatment does not cure or vulcanize the material, does not destroyits plasticity, and does not interfere with its subsequent curingoperation. Accordingly, a further aspect of the invention is thecombination of treatments applied to the polymer including the sulfurchloride treatment and a compounding with sulfur, a sulfurization aid,various pigments and loading agents and a subsequent curing by theapplication of heat into a fully cured and sulfurized material which hasa markedly increased abrasion resistance, a markedly increased flexureresistance; the procedure giving a much greater ease of curing as wellas the capability of curing in the presence of natural rubber and otherunsaturated substances.

Thus, an object of the inventionis to modify the characteristics of aniso-olefin-diolefln polymer by the application thereto of a sulfurchloride; a further object is to apply to an interpoiymer of aniso-olefin with a diolefln, a sulfur chloride treatment, andsubsequently a curing treatment to improve modulus, the abrasionresistance and the flexure resistance of the polymer. Other objects anddetails of the invention will be apparent from the followingdescription.

The polymer material .of this invention is pref- I erably prepared bythe procedure shown in the copending application Serial No. 182,252,filed December 29, 1937, in the name of William J. Sparks and Robert M.Thomas, now Patent No. 2,356,127, of which this application is acontinuation in part. In outline, the procedure for preparing thepolymer consists in preparing a mixture of isobutylene in the proportionof from 70 preferred to 99 parts with a dioleiln in the proportion Of 30to 1 part; suitable dioleflns being butadiene, isoprene, pentadiene,dimethyl butadiene, cyclopentadiene or other conjugated dioleflns. Themixture of isobutylene and conjugated diolefin is then cooled to arelatively low temperature, preferably below -20 C., and preferably bythe application to the mixture of a refrigerant such as solid carbondioxide, or ethylene (which is the refrigerant-diluent) or such otherdiluent refrigerants as liquid methane, especially in admixture withliquid propane or liquid 3 ethane or under suitable conditions, externalcooling may be used. In addition, various diluents may be used such asbutane, ethyl or methyl chloride and the like. If solid carbon dioxideis used, it is preferably present in substantial excess, usually 2 or 3times by weight of the amount of mixed oleflns. If the liquidhydrocarbon refrigerant-diluents are used, they are preferably presentin the proportion of from 2 to 5 volumes per volume of mixed oleflns. Tothis mixture of olefins and diluent-refrigerant there is then added asolution of an active metal halide catalyst such as aluminum chloride,titanium chloride, or uranium chloride dissolved in an inert,low-freezing, carbonaceous solvent such as ethyl or methyl chloride orcarbon disulflde or other similar low freezing, non-complex formingsolvent. The catalyst solution is preferably applied to therapidlystirred olefin-containing mixture in the form of a fine mist orspray onto the rapidly agitated surface of the olefin containingmixture. The polymerization proceeds rapidly to yield a slurry or thesulfurization aid, tetra methyl thiuram disulmass of the polymer in theresidual diluentrefrigerant.

The polymerization reaction is preferably con tinued until from 50% to95% of the oleflns present have reacted. when this stage of reaction isreached, the reaction is desirably quenched by mixing the polymerizationmaterial with a combined-oxygen-containing substance such as an alcohol,a ketone or an acid, or an alkaline agent such as caustic or carbonatesolution or ammonia or other similar quenching agent. The polymer isthen preferably brought up to room temperature and washed to remove thediluent, the refrigerant, the catalyst solvent and the unreacted olefinsas well as the decomposition products of the active metal halidecatalyst substance. This washingis conveniently conducted in a Werner-Pfleiderer type of kneading machine, but it may be conducted in theBanbm'y type of mill or on the open rolls or merely by prolonged soakingin a churn or other simple washing equipment. The polymer is thenpreferably dried and is then ready for the next step of the presentinvention.

EXAMPLEI In practicing the invention, the polymer prepared as abovedescribed is mixed in the. cold with sulfur monochloride, preferablyupon the open roll mill, or in the Banbury mixer or even in theWerner-Pfleiderer mixer. The material is then milled hot, that is. at atemperature of about 100 C. on a closely adjusted roll mill. During thismilling considerable quantities of hydrogen chloride are evolved. Themilling is preferably continued until substantially all vof the hydrogenchloride is driven out, this requiring from 10 to minutes of milling.The material may be cooled on the mill and then, mat a later date, itmay be compounded with appropriate additional substances. v

A suitable compounding formula consists of:

. Parts S201: treated polymer 100 Channel gas black" 50 Zinc oxide 5Stearic acid 3 Sulfur 3 Tetra methyl thiuram disulflde 1 This formula isconveniently prepared by incorporating the successive substances intothe polymer on the open mill in a manner much like that in which rubbercompounding is accomplished. The compounding may be conducted curve,

fide, but the mill is preferably cooled to a temperature well below C.before the sulfurization aid is added. The completed compound is thenplaced in appropriate molds and cured by the application of heat,preferably a temperature of C. and an interval of approximately 60vminutes. The effect of varying amounts of sulfur monochloride upon thecharacteristics of the polymer are shown in Table 1:

'Tssui,

E'flect of quantity of S 81: upon the polymer when cured withtetramethylthiummdisulflde Mme eat Lbalaq. in.

None $000-$400 700-800 4 1,1)0 600 a 1,800 i 600 12 1,880 400 16 2,000876 From this table it will be observed that the treatment of thepolymer material with sulfur monochloride presents a method of obtainingbetter efficiency in consumption of the double bonds in thesulfurization reaction.

In measuring abrasion resistance on the duPont abrader, two factors areimportant, i. e., the amount of loss per horse-power consumed and thecharacter of the abraded surface.- Rubber gives a smooth surface with apowdery abrasion product. The polymer material ordinarily gives a roughsurface with a stringy abrasion product. The very great change in theabrasion resis obtained is shown in Table 2:

TABLE 2 Abrasion of S202: (12%) treated iso-olefin-diolefln interpolvmeron du Pont obradcr It will be observed that this treatment effects avery great improvement in the abrasion resistance.

The treatment likewise very greatly modifies the modulus of elasticity,the effect upon the polymer beng to impart a higher modulus (more.perpendicular stress-strain curve) and obtain a product havingapproximately equivalent .tensile strength. I It is obvious that nosingle stress-strain relationship inherent in a product would be optimumfor all or even a major portion of the uses to which that product mightbe applied. Previous to the present invention, it was not possible tochange by a substantial amount the modulus of materials of this typewithout a deteriorating eflect on other properties. By the applicationof Intheph caltestingofrubber therntiooi'sh'esatostrain, Le. theload lbaors monornioapmamoimmnmsectlonalaieatoproduceastated tioniscalledtbemodulus. Itisameasureof ,Jliniiuencedby gtatiomstateolcure,ualit y oolil'rswrnbbernndothsiactus.

modnlusstanygiven' isshownbythestms-etrain 2,44 ,are

the present invention, it is now m ble to produce moduluscharacteristics in conformity with the demandsof a particular need andthis greatly extends the range of applicability of theiso-olefin-diolefin polymers.

EXAMPLE n Parts by weight Sulfur chloride treated isobutylene-isopreneinterpolymer 100 Carbon black 50 Zinc oxide 5 Stearic acid 3 Sulfur 1.5

These materials are desirably dissolved in 54 naphtha in the proportionof i'part by weight of the polymer mixture to from 3 to parts by weightof the naphtha. This composition is a highly satisfactory cement,particularly for such uses as cementing rubber articles together,cementing polymer articles together, cementing polymer articles torubber articles and cementing either rubber or polymer articles to othermaterials such as metal, wood, leather, fabrics in general, andsimilaruses.

It will be observed that no sulfurization aid is added in the aboveinstances to the cement. The sulfurization aid is not necessary since a.sufficient amount of sulfurization aid diffuses from the tread andcarcass into the cement to complete the curing; or in the case of thepolymer to metal adhesion sufficient sulfurization aid diffuses from thepolymer layer to cure the cement.

Alternatively, however, in some instances it is desirable to add thesulfurization aid to the cement and this is conveniently done in theproportion of approximately 1 parts to -3 or 4 parts of thesulfurization aid per 100 parts of the polymer, if sulfur is alsopresent, or if desired, the sulfur may be omitted, and the curingobtained entirely from the sulfurization aid.

This cement is applicable to the cementing of rubber or polymer articlesto other synthetic rubbers or rubber substitutes includingpolybutadiene, Buna; polybutadiene acrylonitrile, Buna N;polybutadiene-styrene, Buna S; polychloroprene, neoprene; the reactionproduct of ethylene dichloride and sodium polysulfide, and similarsubstances. The cement also is strongly adherent to most of theso-called synthetic plastics'including the phenol formaldehydecondensation resins, the acrylate resins and the many other 0 ing afterthe sulfur chloride treatment and also the sulfur chloride treatedpolymer is still plastic and can still be worked on the mill; still hasa considerable amount of cold flow and is capable or flowing to fill thecontours of a mold upon heating, even though the sulfur chloride hasbeen absorbed into the polymer and combined therewith.

Applicants present opinion is that the sulfur chloride removes a portionof the hydrogen from the polymer without reducing the unsaturation. Itis believed at the present time that in the preparation of the polymer along chain molecule is obtained in whichtheunsaturation of all of theisobutylene molecules except a terminal molecule, disappears and. inwhich the dioleffln molecules are polymerized into the chain with theloss of one of the double bonds as shown in this formula:

Isobutyll (Isobutyl- (Butadiene) (Isohutyletc.

eno) ene) I I one) I It is believed that this chain structure builds upuntil molecular weights of from 15,000 to 150,- 000 are obtained.

It is further believed that when the sulfur monochloricle or sulfurdichloride treatment is applied, both the sulfur and chlorine areabsorbed into the molecule by the double bonds in as two differentmolecules as shown in the following equation:

It will be observed that hydrogen chloride is eliminated by thisreaction and that two of the chain molecules are linkedtogether by asulfur atom while retaining double bonds in each molecule in nearly theoriginal position. It may well be that linkage by a single sulfur atomis different from the curing operation by sulfur. In any event, thematerial produced by this reaction is very different from the curedmaterial. These equations are offered as a possible suggestion of thereaction and as a plausible reason for the 5 differences obtained in thepresent process. They have not, however, been proved, and they are 1 notoffered as settled fact, nor is reliance placed upon them forexplanation of the invention.

Thus, the invention consists of a new and useful process for improvingthe physical characteristics of an oleflnic interpolymer by theapplication to a solid polymer of a substantial percentage of sulfurchloride, and the elimination of hydrogen chloride from the polymer toproduce a material which is capable of being 1 compounded, milled andthereafter cured with sulfur at an elevated temperature to produce amaterial having an elastic limit, a tensile strength, a high elongation,a high abrasion resistance and a high flexure resistance.

The invention claimed is:

1. In the processing of a low temperature interpolymer of a maiorproportion of isobutylene with a minor proportion of a coniugateddiolefln, the said interpolymer having a molecular weight between about15.000 and 150,000 and an iodine number within the range between about 1and 45, the step of treating the polymer with a sulfur chloride,withdrawing hydrogen chloride from the treated polymerand thereaftermilling the material to incorporate thereinto carbon black,

zinc oxide, stearic acid, sulfur and a sulfurization aid.

2. In the processing of a low temperature interpolymer of a majorproportion of insobutyiene and a minor proportion of a eoniugateddiolenn, the said interpolymer having a molecular weight between about15,000 and 150,000 and an iodine number within the range of betweenabout 1 and '45, the steps of milling the polymer, and adding sulfurmonochloride to the milled polymer, and thereafter withdrawing hydrogenchloride.

3. In the processing of a low temperature interpolymer of a majorproportion of isobutylene with a minor proportion of butadiene. the saidinterpolymer having a molecular weight between about 15,000 and 150,000and an iodine number within the range between about 1 and 45, the

step of treating the polymer with a sulfur chloride, withdrawinghydrogenchloride from the treated polymer and thereafter milling the material toincorporate thereinto carbon black, zinc oxide, stearic acid, sulfur anda sulfurization aid.

4. In the processing of a low temperature interpolymer of a majorproportion of isobutyiene with a minor proportion of isoprene, the saidinterpolymer having a molecular weight between 8 number within the rangebetween about 1 and 45, the step of treating the polymer with a sulfurchloride, withdrawing hydrogen chloride from the treated polymer andthereafter milling the material to incorporate thereinto carbon black,zinc oxide, stearic acid, sulfur and a sulfurization aid.

"6. In the processing of a low temperature interpolymer of a majorproportion of isobutylene with a minor proportion of butadiene, the saidinterpolymer having a molecular weight between about 15,000 and 150,000and an iodine number 1 within the range of between about 1 and 45, the

steps of milling the polymer, and adding sulfur monochloride to themilled polymer, and thereafter withdrawing hydrogen chloride.

7. In the processing of a low temperature in- I terpolymer of a majorproportion of isobutylene with a minor proportion of i isoprene, thesaid interpolymer having a molecular weight between about 15,000 and150,000 and an iodine number within the range of between about v1 and45, the steps of milling the polymer, and adding sulfur monochloride tothe milled polymer, and thereafter withdrawing hydrogen chloride.

8. In the processing of a low temperature interpolymer of a majorproportion of isobutylene with a minor proportion of dimethyl butadiene,the said interpolymer having a molecular weight between about 15,000 and150,000 and an iodine number within the range of between about 1 and 45,the steps of milling the polymer, and adding sulfur monochloride to themilled polymer, and thereafter withdrawing hydrogen chloride.

WILLIAM J. SPARKS. ROBERT M. THOMAS.

anrnanucns man The following references are of record in the file ofthispatent:

UNITED STATES PATENTS Number Name Date 2,023,495 Thomas Dec. 10. 19352,138,895 Wiezevich Dec. 6, 1938 2,142,980 Huijser Jan. 3, 19392,152,928 Thomas Apr. 4, 1939 2,213,423 Wiezevich Sept. 3, 1940 1FOREIGN PATENTS Number Country Date 6,642 Great Britain June 21, 1911513,521 Great Britain Oct. 16, 1939

